"Defensively we just weren't desperate enough and positionally we weren't great and that is my responsibility," he said.

"I probably got team selection wrong ... it wasn't my greatest coaching night so I deserve what I get.

"We just didn't look settled defensively at all ... three of the back four, I don't think any of them are settled in their positions yet, so it was too much of an ask."

Melbourne conceded four goals in the initial 32 minutes at Hindmarsh Stadium and Postecoglou admitted ongoing concern at his leaky defence.

The Victory have conceded 20 goals in 10 games, with only last-placed Sydney FC letting in more this season.

"We had a really poor first half defensively and paid a price for it," Postecoglou said.

"I think it's all about our frailties, that is for us to try and address, but we have got to pay credit to Adelaide."

The Victory sorely missed defensive stalwart Mark Milligan, who was on Socceroos duty, and Postecoglou said his absence exposed his club's shallow depth.

"We can't sit here and complain about lack of development of the Socceroos and then complain if some of our guys get an opportunity," he said.

"It's up to each and every squad to get strong enough to withstand that - and we're not.

"If I was to measure us against the best team in the competition at the moment, what we're lacking is depth.

"I hope the Socceroos qualify and we need them to keep getting stronger ... I'm hoping every player who is an Australian in our competition would die for an (international) opportunity and I would never hold them back from that."